1. Field of the invention
This invention relates to thermal expansion joints and more particularly to thermal expansion joints with tabs that flex to minimize thermal deformations.
2. Description of the related art
Large temperature changes in materials can cause large displacements caused by thermal expansion and contraction of the material. The effect is particularly pronounced in connections between two materials with widely differing thermal expansion coefficients. The thermal changes can be caused by frictional aerodynamic heating of aircraft structures, by loading of cryogenic propellants into tanks, or by any number of other causes. The constrained deflections caused by thermal expansions and contractions can generate potentially destructive stresses on the structures of vehicles such as airplanes and rockets.
In the past, a cryogenic tank would be connected to another cryogenic tank or to another structure by an intertank. The difference in the coefficient of thermal expansion between the cooled tank material and the intertank material creates a large thermal stress at the joint therebetween. Typically the thickness of the material at the joint would be increased to prevent buckling of the material which comprises the shell structure of the rocket. However, increasing the thickness of the material at the joint increases the weight of the vehicle. The penalty for carrying the extra weight is a reduced payload to orbit and slower vehicles.
Aircraft traveling at high speeds have the leading edges of their wings become extremely hot compared to the internal structure of the wing due to the aerodynamic flow of air on the leading edge of the wing. The hot leading edge skin of the wing is connected to an internal wing spar. The changes in temperature between the hot leading edge of the wing and the cooler spar causes thermal expansion stress at the joint connecting the skin to the spar. If heavier materials are used to sustain the stress in the connecting joint the aircraft weight will increase, causing the useful load and performance of the aircraft to decrease.